Home brew receiver project

Discussion in 'Homebrew and Kit Projects' started by K6BSU, Jul 10, 2018.

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  1. K6BSU

    K6BSU Ham Member QRZ Page

    This receiver was designed and constructed in 1994, back when I was young and foolish. I had some great ideas for a no-compromise ham band receiver. I had been studying the Vackar VFO circuit, and I wrote an article for QST magazine trying to spark interest in this wonderful VFO circuit. To put the VFO to good use, I designed this receiver around the VFO module, which was then already finished.

    I was not pleased with the receiver in 1994, so it was put back on the shelf. From time to time, I looked at the schematics and puzzled why it wasn't working very well. To make a long story short, I re-visited all the calculations and realized that all the signals driving the Mini-Circuits diode mixers were too weak. After changing the circuit parameters to increase the mixer drives, it worked just as I had hoped. The final effort began several months ago, in 2018. It doesn't normally take 24 years to build a receiver, but it did in this case.

    The circuit diagram is complex, and my pencil drawings don't photograph very well. The basic characteristics of the receiver are:

    Double conversion. 1st I.F. is 1.8 MHz. 2nd I.F. is 455 KHz with switched commercial crystal filters.

    All mixers are Mini-Circuits double-balanced diode-ring mixers.

    The Vackar VFO operates 4.0- 4.3 MHz.

    Plug-in tuning units contain an antenna pre-selector and an up-converter to move the VFO up to the band in use.

    Additional circuits include amplified and delayed AGC, variable notch filter and a crystal calibrator.

    Audio amplifier is a push-pull, 3 Watt circuit using discrete transistors. HF RX 001.jpg HF RX 004.jpg HF RX 005.jpg HF RX 006.jpg HF RX 007.jpg HF RX 008.jpg HF RX 009.jpg HF RX 010.jpg HF RX 011.jpg
     
    WB0RIO, KC9YGN, VE3GZB and 9 others like this.
  2. W5KUL

    W5KUL Ham Member QRZ Page

    That is some nice work!
     
  3. N1OOQ

    N1OOQ Ham Member QRZ Page

    Plug-in band modules, ala TenTec Scout?

    What's that tuning dial?
     
  4. VK4FFAB

    VK4FFAB Subscriber QRZ Page

    Awesome work and thanks for sharing it.
     
  5. N1OOQ

    N1OOQ Ham Member QRZ Page

    Yes, thanks for this. BTW, your schematics reproduced very well, and are pretty easy to follow. Nice job.
     
  6. K6BSU

    K6BSU Ham Member QRZ Page

    The tuning is about 6:1 gear-driven with stock anti-backlash gears. I lathe-turned the bearings, flywheel, and the plastic dial face; marked with India Ink.

    Add. note: All sub-assemblies are on connectors to make it easier to change things.
     
    N1OOQ likes this.
  7. W7UUU

    W7UUU QRZ Lifetime Member #133 Life Member Platinum Subscriber QRZ Page

    Thanks so much for sharing this! It's getting more and more rare to see homebrew receivers anymore, and always a treat

    Dave
    W7UUU
     
  8. K1ZJH

    K1ZJH Ham Member QRZ Page

    Awesome job! Reminds me of what we would see in the old Ham Radio Magazines or in QST back in the sixties!

    Nice work.
     
  9. VE3GZB

    VE3GZB Ham Member QRZ Page

    Sweet!!!
     
  10. AD5HR

    AD5HR Ham Member QRZ Page

    Thanks for posting the rig!
    I've built a few transmitters,but never a receiver.
    Great work, love the plug-in module concept.
    Jon
     

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